Purification of colonic and colonic tumor membranes will be carried out on homogeneous cell populations. The membrane fragments will be compared to transport and fluidity properties. BIBLIOGRAPHIC REFERENCES: Hung, H., Saccomani, G., Rabon, E., Schackmann, R., Sachs, G.: H ion transport by gastric membrane vesicles. Biochim, Biophys. Acta 464: 313-327, 1977. Mihas, A., Sachs, G., Saccomani, G: Antibody against K ion-ATPase from hog gastric mucosa. Clin, Res. 25, 18A, 1977.